Spiders Eat 400-800 Million Tons Of Insects Every Year

Posted: Mar 16 2017, 3:14am CDT | by , in News | Latest Science News

Spiders Eat 400-800 Million Tons of Insects Every Year
Credit: David E. Hill, Peckham Society, Simpsonville, South Carolina

For comparsion, worldwide human population consumes around 400 million tons of meat and fish every year

A new study says that spiders eat up to 800 million metric tons of insects every year - equal to the weight of around 100 elephants. These estimates are astonishing, given the fact that all humans together consume an estimated 400 million tons of meat and fish each year.

The findings, published in journal The Science of Nature, also reflect on how important these eight-legged carnivores are to our ecosystems and how efficiently they are protecting us from countless pests that transmit infections or diseases.

With more than 45,000 species, spiders are one of the most widespread groups of predators. Most of the spiders are found in forests and grasslands while some also exist in crops, deserts and urban areas. Because of their abundance and secretive lifestyle, it was previously difficult to assess their impact on other pests, which ultimately affects our surroundings.

Using data from 65 previous studies, researchers from University of Basel in Switzerland and Lund University in Sweden have found that spider’s total population is around 25 million metric tons.

Researchers then used two simple methods to calculate how much the world's spiders eat annually. In their first approach, they took into account how much spiders generally need to eat to survive while the second approach was based on the prey capture field observations in relation to their population density per square meter. Both methods yielded consistent results and showed that spiders wipe out an estimated 400-800 million tons of prey every year.

Of those, more than 95 percent of the insects are killed by forest and grassland spiders, showing spiders in other habitats as a rather insignificant contributor over a full year. This can be partly explained by the fact that forests and grasslands are not as widespread as cities that allow for greater biomass and less opportunities to prey on.

This study is the first to demonstrate the impact of combined spider community on insects and pest on a global scale.

"Our calculations let us quantify for the first time on a global scale that spiders are major natural enemies of insects. In concert with other insectivorous animals such as ants and birds, they help to reduce the population densities of insects significantly," said lead author Martin Nyffeler from University of Basel.

“Spiders thus make an essential contribution to maintaining the ecological balance of nature.”

Martin Nyffeler & Klaus Birkhofer
An estimated 400-800 million tons of prey are annually killed by the global spider community
The Science of Nature (2017), doi: 10.1007/s00114-017-1440-1

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The Author

<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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